Piston construction



Dec. 21, 1937. w. WUERFEL PISTON CONSTRUCTION 2 Sheets-Sheet 1 Filed June 30, 1933 miiiam like/jag Dec. 21, 1937. W ERFEL 2,102,661

PISTON CONS TRUCTION Filed June 30, 1933 v 2 Sheets-Sheet 2 [NVENT mil Lam erfel.

ATTORNEY UNITED STATES PATENT OFFICE PISTON CONSTRUCTION William Wuerfel, Philadelphia, Pa., assignor to Wilkening Manufacturing Company, Philadelphia, Pa., a corporation of Delaware Application June 30,1933, Serial No. 678,493

Claims. (01. 309-12) The present invention relates to a new and use ful piston and piston constructiomthe lower or skirt portion of which is split longitudinally and is resilientlyexpanded, so as to cause the skirt to expand radially, and also relates to a new and useful method or process of making pistons so as to impart resiliency to the skirt portions thereof.

The object of the present invention is to provide a split-skirt type piston, wherein the skirt is caused to expand outwardly against the cylinder wall by a generally uniform and predetermined force, so as to prevent the skirt from collapsing or fluttering at high piston speed, and so as to maintain the skirt in a'generally round or circular formation.

With the above and other objects in view, which will appear more fully from the following detailed description, the present invention consists in iongitudinally slotting or splitting the skirt or lower portion of the piston, from its lowermost edge up to some point beneath the bottom ring-receiving groove, then slotting the skirt also transversely to a suitable extent at the upper end or head end.

of the longitudinal slot or split, so as to permit a certain amount of expansion and contraction in the split portion of the skirt, providing suitable grooves in the juxtaposed split edges of the skirt, and so positioning a generally corrugated spring member in said groove, as to cause the same to exert a generally tangential force upon the two longitudinal split edges of said skirt, in opposite directions, so as to tend to expand said skirt.

The present invention further consists of other novel details of construction, all as will more fully appear from the following detailed description.

For the purpose of illustrating the invention, there is shown in the accompanying drawings one form thereof which is at present preferred,

since the same has been found in practice to give,

satisfactory and reliable results, although it is to be understood that' the various instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangement and organization of the instrumentalities as herein shown and described.

Referring to the drawings in which like referencecharacters indicate like parts:

Figure 1 represents a front elevational view of a piston embodying the present invention.

Figure Zrepresents a bottom plan view of the same, I

Figure 3 represents a plan view of the corrugated spring member.

Figure 4 represents a perspective view of the' skirt.

cutting tool which may be employed in forming the grooves in the longitudinal split edges of the Figure 5 represents a section which may be referred generally to-line 5--5 of Figure 1, on a much enlarged scale, illustrating a modified embodiment of the present invention, wherein a fiat, waved or corrugated ribbon type spring is employed with the corrugations or undulations being in a generally radial direction instead of tangentially, as in the modification shown in Figures- 1, 2, and 3. I

' Figure 6 represents a section generally on line 5-6 of Figure 5.

Figure 7 is a section similar to that shown in Figure 5, illustrating a further modification of the present invention.

The piston 5, of the present invention, maybe of any suitable type, and formed of any suitable metal, having any suitable number of ring-receiving grooves 6 and having a lower skirt portion Land wrist pin bearings 8 and 9 formed integrally with the piston.

Intermediate the pair of wrist pin bearings 8 and 9, a relatively narrow parallel portion of the piston skirt I is removed by any suitable cutter,

slight gap or space ill in the skirt'l. This leaves the skirt split along one generally longitudinal line. A transverse slot Ii is also provided in the skirt, at the upper end of the gap or slot Ill, so as to give the two halves of the skirt, on either side of the slot l0, greater freedom of expansion and iii. The tool l6 rotated in the head of the milling machine is then fed through the slot III while rotating at a suitable speed, and generally parallel to the slot, so as to form opposed grooves l4 and IS in thefree edges of said slot.

The expander spring I9 is formed of suitable spring wire, of suitable thickness, and is formed with generally similar corrugations 20.

- The upper end 2! of the spring I9 is extended slightly beyond the general outline of the spring, so as to cause said end 2| to project into the slot II to a suitable extent, thereby to lock the spring IS in thegrooves I4 and I5 and to prevent it from sliding out. Thus the spring I9 is insorted merely by slipping it in at the lower end,

-or the piston may be formed initially with the and it is forced into the grooves-l4 and I5 until the slightly enlarged end 2i of. the spring snaps into the transverse slot I I. When thus snapped in place, the spring is effectively locked against any longitudinal displacement. Hence the reciprocation of the piston has no effect upon the security of the springin the piston.

The transverse overall dimension of the spring IS in its normal or unstressed condition is greater than the normal distance between the bottom of the groove 14 and the bottom of the groove l5, by an extent suflicient to tension the spring l9 when inserted into said groove, to the desired extent. When the spring I9 is inserted into grooves l4 and [5, the spring is tensioned trans-.

versely, and exerts a tangential force equal to this tension.

This tangential force exerted generally uniformly throughout the length of the slotted portion of the skirt, causes the skirt to be expanded against the cylinder wall'so as to prevent the collapsing of the piston skirt and to prevent the generally flutter of the piston skirt at high speeds. This also tends to expand the skirt under all operating conditions.

In Figures 5 'and 6, a modified form of the present constructionis illustrated, wherein a flat ribbon type spring member, -25, of generally waved, corrugated orjcrimped form isemployed in the grooves l4 and I5 cut int the .piston skirt 1. and 6, extend generally in a radial direction'l'} that the direct force resulting from thecompres sion of the spring or the partial flattening'outof the corrugations thereof, is exerted in a generally radial directiqnindigated by the arrows 26, while the resultant force is exerted'in a generally tangential direction indicated by the arrows 21. This resultant tangential force is caused by the inclination of the contacting surface of the groove. While in Figures 5 and 6, the groove is shown of curved cross-section, the desired inclination may be produced by the formation of V-shaped grooves instead of grooves of curved or circular cross-section, as indicated in Figure 7; it being necessary for the second embodiment of my invention merely to have inclined side walls to coact with the generally radially expanding spring element.

The invention may be embodied 1 other specific forms without departing from he spirit or essential attributes thereof, and it is desired therefore that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had to the appended claims rather than to the foregoing description to indicate the scope of the invention.

I claim:

1. The combination having the skirt longitudinally and having also a generally transverse slot incommunication with said generally longitudinal'slot near the inner end of the latter (thatds, nearest the head-end of the piston) so as to permit expansion and contraction of said skirt, recesses formed in of said longitudinal slot, and a generally corrugated spring member operatively interposed between the two juxtaposed sides of said generally longitudinal slot, said spring including means extending into and coacting with said recesses for retainingsaid spring member againstgenerally radial displacement in relation to the piston skirt, and including meanscooperating with the walls of said transverse slot to retain said Spr ng ment in relation to the piston skirt.

-The corrugations, as seen iFigures 5 of a trunk type piston portion thereof slotted generally the juxtaposed sides member against generally longitudinal displacement in relation to the piston skirt.

2. The combination of a trunk type piston having the skirt portion thereof slotted generally longitudinally and having also a generally transverse slot in communication with said generally longitudinal slot near the inner end of the latter (that is, nearest the head-end of the piston) so as to permit expansion and contraction of said skirt, and having the skirt-wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portion 01'. the skirtwall, recesses formed in the juxtaposed sides of said longitudinal slot, and a generally corrugated spring member operatively interposed between the two juxtaposed sides of said generallylon'gitudinal slot, said spring including means extendi g into and coacting with said recesses for reta said spring member against generally radial displacement in relation to the piston skirt, and including means -cooperating with the walls of said transverse slot to retain said spring member against generally longitudinal displace- 3. The combination of a trunk type piston having the skirt portion thereof slotted generally longitudinally and having also a generally transverse-slot in communication with said generally longitudinal slot near the inner end of the latter (that is, nearest the'head-end of the piston) so to permit expansion and contraction of said t, recesses formed in the juxtaposed sides of ongitudinal slot, and a generally corrugated sp lll g member operatively interposed between the two juxtaposed sides of said generally longitudinal slot, with its convolutions extending generally tangentially, said spring including means extending into and coacting with said recesses for retaining said-spring member against generally 7 radial displacement inrelation to the piston skirt,

and including means cooperating with the walls of said transverse slot toretain said spring member, against generally longitudinal displacement in relation to the piston skirt.

' 4o 4. The combination of a trunk type piston having the skirt portion thereof slotted generally I longitudinally and having also a generally transverse slot in communication with said generally longitudinal slot near the inncrend of the latter (that is, nearest the head-end of the piston) so as to permit expansion and contraction of said skirt, and having the skirt-wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portion of the skirt-wall,

, recesses formed in the,juxtaposed sides of said longitudinal slot, and a generally corrugated spring member operatively interposed between the two juxtaposed sides of said generally longitudinal slot, with its convolutions extending generally tangentially, said spring including means extending into and coacting with said recesses for retaining said spring member against generally radial displacement in relation'to the piston skirt, and including means cooperating with the walls of said transverse slot to retain said spring mem; ber against generally longitudinal displacement in relation to the piston skirt.

5. A piston having a skirt slotted generally longitudinally. and having opposed parallel grooves in the juxtaposed faces of said longitudinal slo't intermediate. the inner and outer generally cylindrical surfaces of said piston skirt, and of a transverse width substantially less than the principal radial thickness of the major portion of the skirt the longitudinal slot in said skirt extending radially through the skirt wall so as to permit free radial movement of the skirt a portion on each side of the slot with respect to the skirt portion on'the other side of the slot and a corrugated spring member operatively interposed between the two juxtaposed sides of said longitudinal slot and in operative engagement with said grooves, tending to exert opposed tangential forces upon said skirt to expand the, same. 6. A piston having a skirt slotted generally longitudinally and have opposed parallel grooves in the juxtaposed faces of said longitudinal slot, intermediate the inner and outer generally cylindrical surfaces of said piston skirt, and of a transverse width substantially less than the principal radial thickness of the major portion of the skirt, the longitudinal slot in said skirt extending radially through the skirt wall so as to permit.

to expand the same, and with the median portions of said corrugated spring being radially unbounded and clear of the piston skirt wall, and said slotted edges of the piston skirt being in generally pivotal relation to said spring member.

7. A piston having the skirt portion thereof slotted generally longitudinally so as entirely to disconnect the two parts of the skirt on either side of the slot in the zone of the slot and so as to permit the independent radial expansion and contraction of the skirt portions on either side of the slot, recesses formed in the juxtaposed sides Of said longitudinal slot, a generally corrugated spring member operatively interposed between the two juxtaposed sides of said generally longitudinal slot, said spring including means extending into and coacting with said recesses for retain- 50 the piston skirt.

.8. The combinationoi a trunk type piston having a skirt slotted generally longitudinally, and having the skirt wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portion of the skirt wall, a groove provided in each of the opposite side-walls of the slot in said skirt, and a spring member operatively interposed between the slot edges of said skirt within said groove; said skirt having a transverse slot. at the inner end of 'said longitudinal slot (that is, nearest the head-end of the piston) and the'inner end of said spring projecting into said transverse slot.

ing a skirt slotted generally longitudinally at a slight angle with respect to the axis of the piston, said piston skirt alsohaving a transverse slot at the inner end of -said generally longitudinal slot (that is, nearest the head-end of the piston) and communicating therewith, a groove formed in each of the opposite side-walls of the slot in said skirt, and a' generally corrugated spring member interposed betweenthe two sides of the skirt on 9. The combination of a trunk type pistdn hav-,

either side of the slot, said spring member being disposed within said groove, and having its inner end projecting into said transverse slot, thereby to lock the spring against longitudinal displacement while the' piston is in operation.

10. The combination of a trunk type piston having a skirt slotted generally longitudinally and having the skirt wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portion of the skirt wall, a

groove provided in each of the opposite side' walls of the slot in said skirt, and a spring member operatively interposed between the slot edges of said skirt within said groove, said skirt having a transverse slot at the inner end of said longitudinal slot (that is, nearest the head end of the piston} and the inner end of saidspring member projecting beyond the general outline of such member and into said transverse slot for a substantial distance; i

11. The combination of a piston having a skirt slotted generally longitudinally and having the skirt wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portion of the skirt wall, a groove provided in each of the opposite side walls of the slot in said skirt, and a spring member structurally distinct from said piston and having oppositely curved coplanar bends operatively interposed between the slot edges of said skirt within spect to the piston skirt in a radial direction,

without restraining the independent radial expansion and contraction of the skirt portions on opposite sides of the slot.

12. The combination of a piston having a skirt slotted generally longitudinally and having opposed parallel grooves in the juxtaposed faces of said longitudinal slot intermediate the inner and outer generally cylindrical surfaces of said piston skirt, and of a transverse width substantially less than the principal radial'thickness of the major portion of the skirt;-the longitudinal slot in said skirt extending radially through the skirt wall so as to permit free radial movement of the skirt portion on each side of the slot with respect to the skirt portion on the other side of the slot,

and a spring member operatively interposed between the two juxtaposed sides of said longitudinal slot and in operative engagement with said grooves and in generally pivotal relation to the juxtaposed sides of said slot, tending to exert opposed tangential forces uponsaid skirt immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portion of the skirt-wall anda spring operatively interposed between the juxtaposed edges of said slot and in generally pivotal relation to the juxtaposed sides of said slot, thereby to cause said skirt to expand by opposed tangential forces exerted by said spring;-portions of the spring interlocking with portions of the piston for preventing radial displacement of the former with respect to the latter, and. interlocking means a member operatively interposed between the two in generally pivotal relation to the juxtaposed juxtaposed edges of said longitudinal slot and sides of said slot, and thereby to exert opposed tangential forces upon the two opposed sides of saidskirt on either side of said slot;portions of the spring interlocking with portions of the piston for preventing radial displacement of. the former with respect to the latter, and interlocking means for preventing the axial displacement of the spring with respect to the piston.

15. The combination of a piston having a skirt slotted .generally longitudinally and having the skirt wall portions immediately marginal to said slot of generally the same over-all radial thickness as the principal radial thickness of the major portion of the skirt wall, a groove provided in each of the opposite side-walls of the slot in said skirt, and a spring member operatively interposed between the slot edges of said skirt within said grooves, and interlocking with said grooves so as to prevent displacement thereof with respect to the piston skirt in a radial direction,

without restraining the independent radial expansion and contraction of the skirt portions on opposite sides of the slot;said spring being generallycpivotally related to the walls of said wnmAMwUERFEn slot. 

